摘要
大陆内部构造变形和地震活动往往突显出复杂的、区域性的特征,很难用板块构造理论来解释。青藏高原是大陆构造变形的典型实例,具有不同构造变形的分区特征,不仅表现在物质组成、地形地貌和断裂组合等方面的不同,而且还表现出不同的地震活动特征。东昆仑断裂带以北的青藏高原北部地块,主要发育一系列挤压环境下的盆岭构造,表现为以连续变形为特征的上地壳挤压缩短变形;高原中北部巴颜喀拉地块,具有整体向东运动的特点,变形主要集中在其边缘,表现为刚性块体运动特征。在东部,由于稳定的四川盆地(扬子地块)的阻挡,位于龙日坝和龙门山断裂带之间相对坚硬的龙门山地区受到东西向强烈挤压,西部边界为伸展变形;在高原中央腹地羌塘地块西部,由于上地壳物质在向东挤出的驱动下不断变形,沿一系列小型正断层和走滑断层以伸展变形为主,表现为弥散型变形特征。相比之下,羌塘地块的东部向东-南东方向挤出,在大型走滑断层之间形成一个刚性块体;高原南部地块以东西向伸展的南北向裂谷系为主要变形特征,高原南缘以南北向挤压的大型逆冲断裂系为特征。历史地震和仪器记录的大地震(M≥8)只发生在高原东北和东南部的大型走滑带,以及东部和南部边缘的大型逆冲断裂上,沿后者更为频发。到目前为止,高原其他地区只发生了8级以下地震。青藏高原这种分区域的地壳变形形式和地震活动分布是大陆构造变形的重要特征。
The high complexity of tectonic deformation and seismic activity in intracontinental settings cannot be explained by the theory of plate tectonics only.The Tibetan Plateau,extraordinary example of continental tectonic deformation,is characterized by different types of tectonic deformation in different parts of the plateau not only in terms of geology,topography,geomorphology and active faulting,but also in terms of different seismicity characteristics.It can be divided in the following areas:(1)The northern Tibetan Plateau(north of the Kunlun fault),which is under compression while being characterized by a basin and range structure,which formed by a series of thrust faults.There,continuous deformation occurs by upper crustal shortening.(2)The rigid Bayan Har block between the Kunlun and Xianshuihe faults,is characterized by eastward motion of the entire block,with deformation mainly localized along its margins.To the east,the relatively rigid Longmenshan block between the Longriba and Longmenshan faults is strongly compressed due to the stable Sichuan basin.(3)The western part of the central plateau,the Qiangtang terrane,is dominated by extensional deformation along a series of minor normal and strike-slip faults,due to continuous deformation in the upper crust,driven by eastward extrusion.By contrast,the eastern part of the Qiangtang terrane is extruded eastward as a somewhat rigid block between large strike-slip faults.(4)The southern Tibetan plateau is governed by east-west extension thanks to N-S trending rifts.The southern margin of the plateau is characterized by large thrusts.Large historical and instrumental earthquakes(M≥8)only occurred along large strike-slip in the NE and SE parts of the plateau,and along large thrust faults in the eastern and southern margins,very frequent along the latter.In other parts of the plateau,only earthquake of M<8 occurred so far.These different regional crustal deformations and seismic activities are important features of intracontinental tectonic deformation.
作者
李海兵
潘家伟
孙知明
司家亮
裴军令
刘栋梁
Marie-Luce CHEVALIER
王焕
卢海建
郑勇
李春锐
LI Haibing;PAN Jiawei;SUN Zhiming;SI Jialiang;PEI Junling;LIU Dongliang;Marie-Luce CHEVALIER;WANG Huan;LU Haijian;ZHENG Yong;LI Chunrui(Key Laboratory of Deep Earth Dynamics of Ministry of Natural Resources,Institue of Geology,Chinese Academy of Geological Sciences.Beijing,100037;Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou),Guangzhou,511458;Key Laboratory of Paleomagnetism and Tectonic Reconstruction of Ministry of Natural Resources.Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081;Schoolof Earth and Space Sciences,Peking University,Beijing,100871)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2021年第1期194-213,共20页
Acta Geologica Sinica
基金
国家自然科学基金项目(编号41830217,41672211,41941016)
第二次青藏高原综合科学考察研究项目(编号2019QZKK0901)
中国地质调查局项目(编号DD20190059)
南方海洋科学与工程广东省实验室(广州)人才团队引进重大专项(编号GML2019ZD0201)联合资助的成果。
关键词
大陆构造
构造变形
地震活动
地块
青藏高原
continental tectonics
tectonic deformation
seismic activity
block
Tibetan Plateau
